1. Field of the Invention
The present invention relates generally to a heat dissipation device, and more particularly to an improved heat dissipation device assembly with a fan cover for rapidly dissipating heat generated by an electronic element package such as a Central Processing Unit (CPU).
2. Related Art
With the continuing and rapid development of integrated circuits technology, computer has been broadly applied in industry. Along with the increase of requirement of performance, the computer runs faster and faster. The speed of a computer is mainly determined by a CPU installed on a printed circuit board in the computer. Therefore, it is required that the CPU operates at a very high frequency. However, the faster the CPU runs, the more heat it generates. Accumulation of heat at the CPU will lead to an increase of temperature of the CPU, which results in instablity of operation and even destroying the CPU. So the heat must be removed in time so as to keep the temperature of the CPU in a safety range.
A heat sink is generally mounted on the CPU to assist dissipating heat. And a fan is attached to the heat sink for providing a compelled airflow and consequently enhances the efficiency of heat dissipation of the heat sink. There are various construction designs on heat sink assembly with fan in known technology. The related patents comprise U.S. Pat. Nos. D454,947 and 6,535,385, China pat. Nos. 00126321.8 and 01266139.2 etc.
Please refer to FIG. 7. In the disclosure of one above-mentioned patent, a substantially cylindrical heat sink 100 including an erect conductive column and a plurality of fins arranged radially around the conductive column is applied. A plurality of channels is formed between the fins. A fan 200 is fixed on the top end of the conductive column for blowing forced air through the channels between the fins. As any skilled in the art has known, the temperature of the bottom portion of the heat sink 100 near the heat source (such as CPU) 300 is higher than that of the top portion of the heat sink 200 due to heat's being conducted from bottom to top along the conductive column. Airflow provided by the fan 200 will escape from the conductive column during traveling downwardly, which leads to forming of dead space around the bottom portion of the conductive column through which little airflow pass. Therefore, the heat accumulated at the bottom portion of the heat sink 100 near the heat source can not be carried away in time. The fan 200 is not utilized effectively. The accessorial heat dissipating effect of the fan 200 is limited.